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+//===-------- SplitKit.h - Toolkit for splitting live ranges ----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains the SplitAnalysis class as well as mutator functions for
+// live range splitting.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_SPLITKIT_H
+#define LLVM_CODEGEN_SPLITKIT_H
+
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/IndexedMap.h"
+#include "llvm/ADT/IntervalMap.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/CodeGen/SlotIndexes.h"
+
+namespace llvm {
+
+class ConnectedVNInfoEqClasses;
+class LiveInterval;
+class LiveIntervals;
+class LiveRangeEdit;
+class MachineInstr;
+class MachineLoopInfo;
+class MachineRegisterInfo;
+class TargetInstrInfo;
+class TargetRegisterInfo;
+class VirtRegMap;
+class VNInfo;
+class raw_ostream;
+
+/// At some point we should just include MachineDominators.h:
+class MachineDominatorTree;
+template <class NodeT> class DomTreeNodeBase;
+typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode;
+
+
+/// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
+/// opportunities.
+class SplitAnalysis {
+public:
+  const MachineFunction &MF;
+  const VirtRegMap &VRM;
+  const LiveIntervals &LIS;
+  const MachineLoopInfo &Loops;
+  const TargetInstrInfo &TII;
+
+  // Sorted slot indexes of using instructions.
+  SmallVector<SlotIndex, 8> UseSlots;
+
+  /// Additional information about basic blocks where the current variable is
+  /// live. Such a block will look like one of these templates:
+  ///
+  ///  1. |   o---x   | Internal to block. Variable is only live in this block.
+  ///  2. |---x       | Live-in, kill.
+  ///  3. |       o---| Def, live-out.
+  ///  4. |---x   o---| Live-in, kill, def, live-out. Counted by NumGapBlocks.
+  ///  5. |---o---o---| Live-through with uses or defs.
+  ///  6. |-----------| Live-through without uses. Counted by NumThroughBlocks.
+  ///
+  /// Two BlockInfo entries are created for template 4. One for the live-in
+  /// segment, and one for the live-out segment. These entries look as if the
+  /// block were split in the middle where the live range isn't live.
+  ///
+  /// Live-through blocks without any uses don't get BlockInfo entries. They
+  /// are simply listed in ThroughBlocks instead.
+  ///
+  struct BlockInfo {
+    MachineBasicBlock *MBB;
+    SlotIndex FirstUse;   ///< First instr using current reg.
+    SlotIndex LastUse;    ///< Last instr using current reg.
+    bool LiveThrough;     ///< Live in whole block (Templ 5. above).
+    bool LiveIn;          ///< Current reg is live in.
+    bool LiveOut;         ///< Current reg is live out.
+
+    /// isOneInstr - Returns true when this BlockInfo describes a single
+    /// instruction.
+    bool isOneInstr() const {
+      return SlotIndex::isSameInstr(FirstUse, LastUse);
+    }
+  };
+
+private:
+  // Current live interval.
+  const LiveInterval *CurLI;
+
+  /// LastSplitPoint - Last legal split point in each basic block in the current
+  /// function. The first entry is the first terminator, the second entry is the
+  /// last valid split point for a variable that is live in to a landing pad
+  /// successor.
+  SmallVector<std::pair<SlotIndex, SlotIndex>, 8> LastSplitPoint;
+
+  /// UseBlocks - Blocks where CurLI has uses.
+  SmallVector<BlockInfo, 8> UseBlocks;
+
+  /// NumGapBlocks - Number of duplicate entries in UseBlocks for blocks where
+  /// the live range has a gap.
+  unsigned NumGapBlocks;
+
+  /// ThroughBlocks - Block numbers where CurLI is live through without uses.
+  BitVector ThroughBlocks;
+
+  /// NumThroughBlocks - Number of live-through blocks.
+  unsigned NumThroughBlocks;
+
+  /// DidRepairRange - analyze was forced to shrinkToUses().
+  bool DidRepairRange;
+
+  SlotIndex computeLastSplitPoint(unsigned Num);
+
+  // Sumarize statistics by counting instructions using CurLI.
+  void analyzeUses();
+
+  /// calcLiveBlockInfo - Compute per-block information about CurLI.
+  bool calcLiveBlockInfo();
+
+public:
+  SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis,
+                const MachineLoopInfo &mli);
+
+  /// analyze - set CurLI to the specified interval, and analyze how it may be
+  /// split.
+  void analyze(const LiveInterval *li);
+
+  /// didRepairRange() - Returns true if CurLI was invalid and has been repaired
+  /// by analyze(). This really shouldn't happen, but sometimes the coalescer
+  /// can create live ranges that end in mid-air.
+  bool didRepairRange() const { return DidRepairRange; }
+
+  /// clear - clear all data structures so SplitAnalysis is ready to analyze a
+  /// new interval.
+  void clear();
+
+  /// getParent - Return the last analyzed interval.
+  const LiveInterval &getParent() const { return *CurLI; }
+
+  /// getLastSplitPoint - Return that base index of the last valid split point
+  /// in the basic block numbered Num.
+  SlotIndex getLastSplitPoint(unsigned Num) {
+    // Inline the common simple case.
+    if (LastSplitPoint[Num].first.isValid() &&
+        !LastSplitPoint[Num].second.isValid())
+      return LastSplitPoint[Num].first;
+    return computeLastSplitPoint(Num);
+  }
+
+  /// isOriginalEndpoint - Return true if the original live range was killed or
+  /// (re-)defined at Idx. Idx should be the 'def' slot for a normal kill/def,
+  /// and 'use' for an early-clobber def.
+  /// This can be used to recognize code inserted by earlier live range
+  /// splitting.
+  bool isOriginalEndpoint(SlotIndex Idx) const;
+
+  /// getUseBlocks - Return an array of BlockInfo objects for the basic blocks
+  /// where CurLI has uses.
+  ArrayRef<BlockInfo> getUseBlocks() const { return UseBlocks; }
+
+  /// getNumThroughBlocks - Return the number of through blocks.
+  unsigned getNumThroughBlocks() const { return NumThroughBlocks; }
+
+  /// isThroughBlock - Return true if CurLI is live through MBB without uses.
+  bool isThroughBlock(unsigned MBB) const { return ThroughBlocks.test(MBB); }
+
+  /// getThroughBlocks - Return the set of through blocks.
+  const BitVector &getThroughBlocks() const { return ThroughBlocks; }
+
+  /// getNumLiveBlocks - Return the number of blocks where CurLI is live.
+  unsigned getNumLiveBlocks() const {
+    return getUseBlocks().size() - NumGapBlocks + getNumThroughBlocks();
+  }
+
+  /// countLiveBlocks - Return the number of blocks where li is live. This is
+  /// guaranteed to return the same number as getNumLiveBlocks() after calling
+  /// analyze(li).
+  unsigned countLiveBlocks(const LiveInterval *li) const;
+
+  typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
+
+  /// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
+  /// having CurLI split to a new live interval. Return true if Blocks can be
+  /// passed to SplitEditor::splitSingleBlocks.
+  bool getMultiUseBlocks(BlockPtrSet &Blocks);
+};
+
+
+/// SplitEditor - Edit machine code and LiveIntervals for live range
+/// splitting.
+///
+/// - Create a SplitEditor from a SplitAnalysis.
+/// - Start a new live interval with openIntv.
+/// - Mark the places where the new interval is entered using enterIntv*
+/// - Mark the ranges where the new interval is used with useIntv* 
+/// - Mark the places where the interval is exited with exitIntv*.
+/// - Finish the current interval with closeIntv and repeat from 2.
+/// - Rewrite instructions with finish().
+///
+class SplitEditor {
+  SplitAnalysis &SA;
+  LiveIntervals &LIS;
+  VirtRegMap &VRM;
+  MachineRegisterInfo &MRI;
+  MachineDominatorTree &MDT;
+  const TargetInstrInfo &TII;
+  const TargetRegisterInfo &TRI;
+
+  /// Edit - The current parent register and new intervals created.
+  LiveRangeEdit *Edit;
+
+  /// Index into Edit of the currently open interval.
+  /// The index 0 is used for the complement, so the first interval started by
+  /// openIntv will be 1.
+  unsigned OpenIdx;
+
+  typedef IntervalMap<SlotIndex, unsigned> RegAssignMap;
+
+  /// Allocator for the interval map. This will eventually be shared with
+  /// SlotIndexes and LiveIntervals.
+  RegAssignMap::Allocator Allocator;
+
+  /// RegAssign - Map of the assigned register indexes.
+  /// Edit.get(RegAssign.lookup(Idx)) is the register that should be live at
+  /// Idx.
+  RegAssignMap RegAssign;
+
+  typedef DenseMap<std::pair<unsigned, unsigned>, VNInfo*> ValueMap;
+
+  /// Values - keep track of the mapping from parent values to values in the new
+  /// intervals. Given a pair (RegIdx, ParentVNI->id), Values contains:
+  ///
+  /// 1. No entry - the value is not mapped to Edit.get(RegIdx).
+  /// 2. Null - the value is mapped to multiple values in Edit.get(RegIdx).
+  ///    Each value is represented by a minimal live range at its def.
+  /// 3. A non-null VNInfo - the value is mapped to a single new value.
+  ///    The new value has no live ranges anywhere.
+  ValueMap Values;
+
+  typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair;
+  typedef IndexedMap<LiveOutPair, MBB2NumberFunctor> LiveOutMap;
+
+  // LiveOutCache - Map each basic block where a new register is live out to the
+  // live-out value and its defining block.
+  // One of these conditions shall be true:
+  //
+  //  1. !LiveOutCache.count(MBB)
+  //  2. LiveOutCache[MBB].second.getNode() == MBB
+  //  3. forall P in preds(MBB): LiveOutCache[P] == LiveOutCache[MBB]
+  //
+  // This is only a cache, the values can be computed as:
+  //
+  //  VNI = Edit.get(RegIdx)->getVNInfoAt(LIS.getMBBEndIdx(MBB))
+  //  Node = mbt_[LIS.getMBBFromIndex(VNI->def)]
+  //
+  // The cache is also used as a visited set by extendRange(). It can be shared
+  // by all the new registers because at most one is live out of each block.
+  LiveOutMap LiveOutCache;
+
+  // LiveOutSeen - Indexed by MBB->getNumber(), a bit is set for each valid
+  // entry in LiveOutCache.
+  BitVector LiveOutSeen;
+
+  /// LiveInBlock - Info for updateSSA() about a block where a register is
+  /// live-in.
+  /// The updateSSA caller provides DomNode and Kill inside MBB, updateSSA()
+  /// adds the computed live-in value.
+  struct LiveInBlock {
+    // Dominator tree node for the block.
+    // Cleared by updateSSA when the final value has been determined.
+    MachineDomTreeNode *DomNode;
+
+    // Live-in value filled in by updateSSA once it is known.
+    VNInfo *Value;
+
+    // Position in block where the live-in range ends, or SlotIndex() if the
+    // range passes through the block.
+    SlotIndex Kill;
+
+    LiveInBlock(MachineDomTreeNode *node) : DomNode(node), Value(0) {}
+  };
+
+  /// LiveInBlocks - List of live-in blocks used by findReachingDefs() and
+  /// updateSSA(). This list is usually empty, it exists here to avoid frequent
+  /// reallocations.
+  SmallVector<LiveInBlock, 16> LiveInBlocks;
+
+  /// defValue - define a value in RegIdx from ParentVNI at Idx.
+  /// Idx does not have to be ParentVNI->def, but it must be contained within
+  /// ParentVNI's live range in ParentLI. The new value is added to the value
+  /// map.
+  /// Return the new LI value.
+  VNInfo *defValue(unsigned RegIdx, const VNInfo *ParentVNI, SlotIndex Idx);
+
+  /// markComplexMapped - Mark ParentVNI as complex mapped in RegIdx regardless
+  /// of the number of defs.
+  void markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI);
+
+  /// defFromParent - Define Reg from ParentVNI at UseIdx using either
+  /// rematerialization or a COPY from parent. Return the new value.
+  VNInfo *defFromParent(unsigned RegIdx,
+                        VNInfo *ParentVNI,
+                        SlotIndex UseIdx,
+                        MachineBasicBlock &MBB,
+                        MachineBasicBlock::iterator I);
+
+  /// extendRange - Extend the live range of Edit.get(RegIdx) so it reaches Idx.
+  /// Insert PHIDefs as needed to preserve SSA form.
+  void extendRange(unsigned RegIdx, SlotIndex Idx);
+
+  /// findReachingDefs - Starting from MBB, add blocks to LiveInBlocks until all
+  /// reaching defs for LI are found.
+  /// @param LI   Live interval whose value is needed.
+  /// @param MBB  Block where LI should be live-in.
+  /// @param Kill Kill point in MBB.
+  /// @return Unique value seen, or NULL.
+  VNInfo *findReachingDefs(LiveInterval *LI, MachineBasicBlock *MBB,
+                           SlotIndex Kill);
+
+  /// updateSSA - Compute and insert PHIDefs such that all blocks in
+  // LiveInBlocks get a known live-in value. Add live ranges to the blocks.
+  void updateSSA();
+
+  /// transferValues - Transfer values to the new ranges.
+  /// Return true if any ranges were skipped.
+  bool transferValues();
+
+  /// extendPHIKillRanges - Extend the ranges of all values killed by original
+  /// parent PHIDefs.
+  void extendPHIKillRanges();
+
+  /// rewriteAssigned - Rewrite all uses of Edit.getReg() to assigned registers.
+  void rewriteAssigned(bool ExtendRanges);
+
+  /// deleteRematVictims - Delete defs that are dead after rematerializing.
+  void deleteRematVictims();
+
+public:
+  /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
+  /// Newly created intervals will be appended to newIntervals.
+  SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
+              MachineDominatorTree&);
+
+  /// reset - Prepare for a new split.
+  void reset(LiveRangeEdit&);
+
+  /// Create a new virtual register and live interval.
+  /// Return the interval index, starting from 1. Interval index 0 is the
+  /// implicit complement interval.
+  unsigned openIntv();
+
+  /// currentIntv - Return the current interval index.
+  unsigned currentIntv() const { return OpenIdx; }
+
+  /// selectIntv - Select a previously opened interval index.
+  void selectIntv(unsigned Idx);
+
+  /// enterIntvBefore - Enter the open interval before the instruction at Idx.
+  /// If the parent interval is not live before Idx, a COPY is not inserted.
+  /// Return the beginning of the new live range.
+  SlotIndex enterIntvBefore(SlotIndex Idx);
+
+  /// enterIntvAfter - Enter the open interval after the instruction at Idx.
+  /// Return the beginning of the new live range.
+  SlotIndex enterIntvAfter(SlotIndex Idx);
+
+  /// enterIntvAtEnd - Enter the open interval at the end of MBB.
+  /// Use the open interval from he inserted copy to the MBB end.
+  /// Return the beginning of the new live range.
+  SlotIndex enterIntvAtEnd(MachineBasicBlock &MBB);
+
+  /// useIntv - indicate that all instructions in MBB should use OpenLI.
+  void useIntv(const MachineBasicBlock &MBB);
+
+  /// useIntv - indicate that all instructions in range should use OpenLI.
+  void useIntv(SlotIndex Start, SlotIndex End);
+
+  /// leaveIntvAfter - Leave the open interval after the instruction at Idx.
+  /// Return the end of the live range.
+  SlotIndex leaveIntvAfter(SlotIndex Idx);
+
+  /// leaveIntvBefore - Leave the open interval before the instruction at Idx.
+  /// Return the end of the live range.
+  SlotIndex leaveIntvBefore(SlotIndex Idx);
+
+  /// leaveIntvAtTop - Leave the interval at the top of MBB.
+  /// Add liveness from the MBB top to the copy.
+  /// Return the end of the live range.
+  SlotIndex leaveIntvAtTop(MachineBasicBlock &MBB);
+
+  /// overlapIntv - Indicate that all instructions in range should use the open
+  /// interval, but also let the complement interval be live.
+  ///
+  /// This doubles the register pressure, but is sometimes required to deal with
+  /// register uses after the last valid split point.
+  ///
+  /// The Start index should be a return value from a leaveIntv* call, and End
+  /// should be in the same basic block. The parent interval must have the same
+  /// value across the range.
+  ///
+  void overlapIntv(SlotIndex Start, SlotIndex End);
+
+  /// finish - after all the new live ranges have been created, compute the
+  /// remaining live range, and rewrite instructions to use the new registers.
+  /// @param LRMap When not null, this vector will map each live range in Edit
+  ///              back to the indices returned by openIntv.
+  ///              There may be extra indices created by dead code elimination.
+  void finish(SmallVectorImpl<unsigned> *LRMap = 0);
+
+  /// dump - print the current interval maping to dbgs().
+  void dump() const;
+
+  // ===--- High level methods ---===
+
+  /// splitSingleBlock - Split CurLI into a separate live interval around the
+  /// uses in a single block. This is intended to be used as part of a larger
+  /// split, and doesn't call finish().
+  void splitSingleBlock(const SplitAnalysis::BlockInfo &BI);
+
+  /// splitSingleBlocks - Split CurLI into a separate live interval inside each
+  /// basic block in Blocks.
+  void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);
+
+  /// splitLiveThroughBlock - Split CurLI in the given block such that it
+  /// enters the block in IntvIn and leaves it in IntvOut. There may be uses in
+  /// the block, but they will be ignored when placing split points.
+  ///
+  /// @param MBBNum      Block number.
+  /// @param IntvIn      Interval index entering the block.
+  /// @param LeaveBefore When set, leave IntvIn before this point.
+  /// @param IntvOut     Interval index leaving the block.
+  /// @param EnterAfter  When set, enter IntvOut after this point.
+  void splitLiveThroughBlock(unsigned MBBNum,
+                             unsigned IntvIn, SlotIndex LeaveBefore,
+                             unsigned IntvOut, SlotIndex EnterAfter);
+
+  /// splitRegInBlock - Split CurLI in the given block such that it enters the
+  /// block in IntvIn and leaves it on the stack (or not at all). Split points
+  /// are placed in a way that avoids putting uses in the stack interval. This
+  /// may require creating a local interval when there is interference.
+  ///
+  /// @param BI          Block descriptor.
+  /// @param IntvIn      Interval index entering the block. Not 0.
+  /// @param LeaveBefore When set, leave IntvIn before this point.
+  void splitRegInBlock(const SplitAnalysis::BlockInfo &BI,
+                       unsigned IntvIn, SlotIndex LeaveBefore);
+
+  /// splitRegOutBlock - Split CurLI in the given block such that it enters the
+  /// block on the stack (or isn't live-in at all) and leaves it in IntvOut.
+  /// Split points are placed to avoid interference and such that the uses are
+  /// not in the stack interval. This may require creating a local interval
+  /// when there is interference.
+  ///
+  /// @param BI          Block descriptor.
+  /// @param IntvOut     Interval index leaving the block.
+  /// @param EnterAfter  When set, enter IntvOut after this point.
+  void splitRegOutBlock(const SplitAnalysis::BlockInfo &BI,
+                        unsigned IntvOut, SlotIndex EnterAfter);
+};
+
+}
+
+#endif